The Association of Arachnoid Cysts and Focal Epilepsy: Hospital Based Case Control Study

Objective: Arachnoid cysts (ACs) are common findings in brain MRI. Our aim was to examine frequency and distribution of ACs in patients with focal epilepsy, compared to healthy control subjects, and to investigate the association of AC and electro-clinical features of focal epilepsy.

Patients And Methods: We performed a retrospective case-control study, using data from 180 patients that underwent video-EEG monitoring between 2009 and 2012, and of 114 healthy controlled subjects. Analysis of electro-clinical data and structural MRI images was conducted.

Results: A significantly higher proportion of ACs in the focal epilepsy group (19/180; 10.5%) compared to healthy control subjects (3/114; 2.6%) (p=0.012) was identified. Significant congruence of semiological features or interictal and ictal EEG with AC localization was identified in only one MRI nonlesional patient with temporal cyst localization.

Conclusion: ACs are seen more often in patients with focal epilepsy. Explicit association between focal epilepsy and AC is possible but exceptional. More likely, focal epilepsy and AC share a common etiological ancestor but represent distant and distinct entities.